1. Technical Field
The present invention relates to the field of thin film write heads.
2. Background Art
Data is stored on magnetic media by writing on the magnetic media using a write head. Magnetic media can be formed in any number of ways, such as tape, floppy diskette, and hard disk. Writing involves storing a data bit by utilizing magnetic flux to set the magnetic moment of a particular area on the magnetic media. The state of the magnetic moment is later read, using a read head, to retrieve the stored information.
Data density is determined by the amount of data stored on an area of magnetic media and depends on how much area must be allocated to each bit. To decrease bit size, head size is decreased by fabricating thin film read and write heads. Thin film heads commonly employ separate write and read heads.
Thin film write heads are typically formed by depositing and etching layers of magnetic, non-magnetic, dielectric, and electrically conductive materials to form the structures of the head. The structures of the head, such as a core, conductors, a yoke, and pole tips, are fabricated in separate steps. This allows the pole tip size to be reduced, thereby reducing the area occupied by the magnetic bits on the media and improving data density. As data bits are placed closer together, larger magnetic flux is required to set the bits to prevent them from inadvertently being changed by adjacent bits, or by stray magnetic flux.
The yoke structure is used to couple the much larger core to the upper of the pole tips. Typically, the yoke is deposited over the top of the conductor layer to attach to the pole tip below. The yoke channels the flux from the larger core into the small pole tip. As the yoke structure narrows and connects to the much smaller pole tip, the flux from the core is channeled into an ever narrowing yoke as it connects to the pole tip.
As ever smaller structures must handle higher magnetic flux, the write head structures, and in particular the yoke structure, become susceptible to saturation. As a result, it is necessary to form the yoke of a material with a sufficiently high magnetic moment to handle high flux density without saturating.
A problem with high magnetic moment material is that imperfections in the uniformity of the material can cause the permeability of the material to degrade. If the imperfections, usually formed during the deposition process, are in an area of high flux density, saturation can occur.
In addition to reducing the size of the write head structures to improve data density, structures of write heads are made small to improve operating frequency. For example, the conductors commonly are located as close as possible to the pole tips to decrease flux path inductance by reducing the length of the flux path. Toward this end, the yoke commonly is joined or stitched to the top of the pole tip so that along with the pole tip, it forms part of the air bearing surface of the write head. An example of such a geometry is disclosed in U.S. Pat. No. 5,649,351 by Cole, et al., issued on Jul. 22, 1997, entitled METHOD OF MAKING THIN FILM MAGNETIC WRITE HEAD, herein incorporated by reference in its entirety. Stitching to the top of the pole tip, however, has drawbacks.
One problem with forming the stitch along the air bearing surface is that, in addition to the primary write gap which is formed to write data to the media, a second write gap could form at the yoke/pole tip interface. The second write gap could form if there are discontinuities at the interface caused by incomplete removal of materials or oxide formation prior to stitching the yoke to the pole tip.
The present invention provides an write head having an improved upper pole tip-to-yoke stitch. The upper pole tip is formed having an open faced sloping surface at an end of the pole tip distal from an air bearing surface. The sloping surface may be formed by conventional techniques such as ion milling to remove a corner portion of the upper pole tip. Preferably the angle of the sloping surface is between 25 degrees and 45 degrees, with the optimum angle being about 30 degrees.
The sloping surface provides a shallow angle for depositing the yoke material over. The shallow angle improves the magnetic properties of the yoke material, particularly in the case of sputtered high moment magnetic materials, and improves the flux flow path through the yoke. As such, the present invention allows conductor coils to be located closer to the air bearing surface without sacrificing yoke material properties and flux flow.
The upper pole tip may have a back portion which is formed over an insulation layer located between a write gap layer and a conductor layer. Preferably the insulation layer and the conductor layer or layers are formed having sloping edges with shallow angles. Preferably the angle of the sloping edges is between 25 degrees and 45 degrees, with the optimum angle being about 30 degrees.
An advantage of the present invention is that it allows the yoke and the yoke-to-pole tip stitch to be recessed from the air bearing surface, if desired, to prevent the yoke or yoke-to-pole stitch from inadvertently writing to the media.